attn: advanced gearheads: Bad Steering Rack?

[LED-Maniac]

OK so Im starting to think my steering rack is bad after I had my alighnment done to cure a "high-speed-wander" problem is it never went away. The ball joint and tie rods feel solid..alignment is perfect, wheel pressures by the book.....when i get up to 70+ there is a slight wander i can just feel it within 5mm of left or right turn....a very faint disconnected feeling where the car moves withing the lane and constant correction is needed lol its friggin annoying. I know these worm drive racks are bullet proof by design but im starting to think that I got a fluke rack which isnt to spec. And since the mechs cant take this car up to highways speeds to verify this problem is there any test to confirm a bad steering rack to help convince them that there is an issue. BTW they never looked at the rack last time....shoulda told them but ill anticipate they cant go up to 70mph to check it next time. I just wanna go in there with proof and not look like a nut and keep saying the rack is in bad shape on a new car lol. any idea or advice...or even similar situation with ur tC?

[reagulator]

I think the problem you are having is bump-steer. This is due to poor suspension design rather then a crappy steering rack. Bump steer is caused when the lower control arm travels in a differn radius then the steering link.

Lets say that the lower control arm travels in a "C" shaped radius. And the steering link also travels in a "C" shaped radius. But the two radii are offsetted to a certain degree that causes the top parts of the two radii to meet at the top and the bottom parts of the radii to be far apart. ( I know this is hard to follow) so i drew a Picture
http://www.imagestation.com/album/pi...23448267&idx=1
What this shows is that when ever your suspension travels up the steering will want to turn inwards because the streering link is physically being pushed in by the control arm, and visa versa.
One way to solve this problem is to lower the steering link with some sort of arm type thing that lowers the linkage.

How do you get the linkage? No idea. Hopefully someone can answer this for me

[LED-Maniac]

WOW awesome response and thanks for the drawing! You made it super clear to me the issue here @ hand. I do feel this bump steer is exagerated when going around uneven road surfaces or dips in the road, especially while turning since I can feel it the most then.

Now to ask you another question.....with all those suspension mods you have on your tC, has the bump steer gotten better, worse, or stayed the same?

[reagulator]

The bump steer is definetly still present but i think the sway bars helped out slightly but it might just be in my head. Keep in mind that sway bars are not designed to cure bump steer.